Chapter 8 – Review

8.1 Writing and Balancing Chemical Equations

  1. What does it mean to say an equation is balanced? Why is it important for an equation to be balanced? Check Answer: [1]
  2. Balance the following equations: Check Answer: [2]
    1. [latex]\text{PCl}_5(s) + \text{H}_2 \text{O}(l) \longrightarrow \text{POCl}_3(l) + \text{HCl}(aq)[/latex]
    2. [latex]\text{Cu}(s) + \text{HNO}_3(aq) \longrightarrow \text{Cu(NO}_3)_2(aq) + \text{H}_2 \text{O}(l) + \text{NO}(g)[/latex]
    3. [latex]\text{H}_2(g) + \text{I}_2(s) \longrightarrow \text{HI}(s)[/latex]
    4. [latex]\text{Fe}(s) + \text{O}_2(g) \longrightarrow \text{Fe}_2 \text{O}_3(s)[/latex]
    5. [latex]\text{Na}(s) + \text{H}_2 \text{O}(l) \longrightarrow \text{NaOH}(aq) + \text{H}_2(g)[/latex]
    6. [latex]\text{(NH}_4)_2 \text{Cr}_2\text{O}_7(s) \longrightarrow \text{Cr}_2\text{O}_3(s) + \text{N}_2(g) + \text{H}_2 \text{O}(g)[/latex]
    7. [latex]\text{P}_4(s) + \text{Cl}_2(g) \longrightarrow \text{PCl}_3(l)[/latex]
    8. [latex]\text{PtCl}_4(s) \longrightarrow \text{Pt}(s) + \text{Cl}_2(g)[/latex]
  3. Balance the following equations:
    1. [latex]\text{Ag}(s) + \text{H}_2 \text{S}(g) + \text{O}_2(g) \longrightarrow \text{Ag}_2 \text{S}(s) + \text{H}_2 \text{O}(l)[/latex]
    2. [latex]\text{P}_4(s) + \text{O}_2(g) \longrightarrow \text{P}_4 \text{O}_{10}(s)[/latex]
    3. [latex]\text{Pb}(s) + \text{H}_2 \text{O}(l) + \text{O}_2(g) \longrightarrow \text{Pb(OH)}_2(s)[/latex]
    4. [latex]\text{Fe}(s) + \text{H}_2 \text{O}(l) \longrightarrow \text{Fe}_3 \text{O}_4(s) + \text{H}_2(g)[/latex]
    5. [latex]\text{Sc}_2 \text{O}_3(s) + \text{SO}_3(l) \longrightarrow \text{Sc}_2 \text{(SO}_4)_3(s)[/latex]
    6. [latex]\text{Ca}_3 \text{(PO}_4)_2(aq) + \text{H}_3 \text{PO}_4(aq) \longrightarrow \text{Ca(H}_2 \text{PO}_4)_2(aq)[/latex]
    7. [latex]\text{Al}(s) + \text{H}_2 \text{SO}_4(aq) \longrightarrow \text{Al}_2 \text{(SO}_4)_3(s) + \text{H}_2(g)[/latex]
    8. [latex]\text{TiCl}_4(s) + \text{H}_2 \text{O}(g) \longrightarrow \text{TiO}_2(s) + \text{HCl}(g)[/latex]
  4. Write a balanced molecular equation describing each of the following chemical reactions. Check Answer: [3]
    1. Solid calcium carbonate is heated and decomposes to solid calcium oxide and carbon dioxide gas.
    2. Gaseous butane, C4H10, reacts with diatomic oxygen gas to yield gaseous carbon dioxide and water vapour.
    3. Aqueous solutions of magnesium chloride and sodium hydroxide react to produce solid magnesium hydroxide and aqueous sodium chloride.
    4. Water vapour reacts with sodium metal to produce solid sodium hydroxide and hydrogen gas.
  5. Write a balanced equation describing each of the following chemical reactions.
    1. Solid potassium chlorate, KClO3, decomposes to form solid potassium chloride and diatomic oxygen gas.
    2. Solid aluminum metal reacts with solid diatomic iodine to form solid Al2I6.
    3. When solid sodium chloride is added to aqueous sulfuric acid, hydrogen chloride gas and aqueous sodium sulfate are produced.
    4. Aqueous solutions of phosphoric acid and potassium hydroxide react to produce aqueous potassium dihydrogen phosphate and liquid water.
  6. Colourful fireworks often involve the decomposition of barium nitrate and potassium chlorate and the reaction of the metals magnesium, aluminum, and iron with oxygen. Check Answer: [4]
    1. Write the formulas of barium nitrate and potassium chlorate.
    2. The decomposition of solid potassium chlorate leads to the formation of solid potassium chloride and diatomic oxygen gas. Write an equation for the reaction.
    3. The decomposition of solid barium nitrate leads to the formation of solid barium oxide, diatomic nitrogen gas, and diatomic oxygen gas. Write an equation for the reaction.
    4. Write separate equations for the reactions of the solid metals magnesium, aluminum, and iron with diatomic oxygen gas to yield the corresponding metal oxides. (Assume the iron oxide contains Fe3+ ions.)

8.2 Classifying Composition, Decomposition and Combustion Reactions

  1. Which is a composition reaction and which is not? Check Answer: [5]
    1. NaCl + AgNO3 → AgCl + NaNO3
    2. CaO + CO2 → CaCO3
  2. Which is a composition reaction and which is not?
    1. H2 + Cl2 → 2 HCl
    2. 2 HBr + Cl2 → 2 HCl + Br2
  3. Which is a composition reaction and which is not? Check Answer: [6]
    1. 2 SO2 + O2 → 2 SO3
    2. 6 C + 3 H2 → C6H6
  4. Which is a composition reaction and which is not?
    1. 4 Na + 2 C + 3 O2 → 2 Na2CO3
    2. Na2CO3 → Na2O + CO2
  5. Which is a decomposition reaction and which is not? Check Answer: [7]
    1. HCl + NaOH → NaCl + H2O
    2. CaCO3 → CaO + CO2
  6. Which is a decomposition reaction and which is not?
    1. 3 O2 → 2 O3
    2. 2 KClO3 → 2 KCl + 3 O2
  7. Which is a decomposition reaction and which is not? Check Answer: [8]
    1. Na2O + CO2 → Na2CO3
    2. H2SO3 → H2O + SO2
  8. Which is a decomposition reaction and which is not?
    1. 2 C7H5N3O6 → 3 N2 + 5 H2O + 7 CO + 7 C
    2. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
  9. Which is a combustion reaction and which is not? Check Answer: [9]
    1. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
    2. 2 Fe2S3 + 9 O2 → 2 Fe2O3 + 6 SO2
  10. Which is a combustion reaction and which is not?
    1. CH4 + 2 F2 → CF4 + 2 H2
    2. 2 H2 + O2 → 2 H2O
  11. Which is a combustion reaction and which is not? Check Answer: [10]
    1. P4 + 5 O2 → 2 P2O5
    2. 2 Al2S3 + 9 O2 → 2 Al2O3 + 6 SO2
  12. Which is a combustion reaction and which is not?
    1. C2H4 + O2 → C2H4O2
    2. C2H4 + Cl2 → C2H4Cl2
  13. Is it possible for a composition reaction to also be a combustion reaction? Give an example to support your case. Check Answer: [11]
  14. Is it possible for a decomposition reaction to also be a combustion reaction? Give an example to support your case.
  15. Complete and balance each combustion equation. Check Answer: [12]
    1. C4H9OH + O2 → ?
    2. CH3NO2 + O2 → ?
  16. Complete and balance each combustion equation.
    1. B2H6 + O2 → ? (The oxide of boron formed is B2O3.)
    2. Al2S3 + O2 → ? (The oxide of sulfur formed is SO2.)
    3. Al2S3 + O2 → ? (The oxide of sulfur formed is SO3.)

8.3 Classifying and Completing Single- and Double-Displacement Reactions

  1. What are the general characteristics that help you recognize single-replacement reactions? Check Answer: [13]
  2. What are the general characteristics that help you recognize double-replacement reactions?
  3. Assuming that each single-replacement reaction occurs, predict the products and write each balanced chemical equation. Check Answer: [14]
    1. Zn + Fe(NO3)2 → ?
    2. F2 + FeI3 → ?
  4. Assuming that each single-replacement reaction occurs, predict the products and write each balanced chemical equation.
    1. Li + MgSO4 → ?
    2. NaBr + Cl2 → ?
  5. Assuming that each single-replacement reaction occurs, predict the products and write each balanced chemical equation. Check Answer: [15]
    1. Sn + H2SO4 → ?
    2. Al + NiBr2 → ?
  6. Assuming that each single-replacement reaction occurs, predict the products and write each balanced chemical equation.
    1. Mg + HCl → ?
    2. HI + Br2 → ?
  7. Use the periodic table or the activity series to predict if each single-replacement reaction will occur and, if so, write a balanced chemical equation. Check Answer: [16]
    1. FeCl2 + Br2 → ?
    2. Fe(NO3)3 + Al → ?
  8. Use the periodic table or the activity series to predict if each single-replacement reaction will occur and, if so, write a balanced chemical equation.
    1. Zn + Fe3(PO4)2 → ?
    2. Ag + HNO3 → ?
  9. Use the periodic table or the activity series to predict if each single-replacement reaction will occur and, if so, write a balanced chemical equation. Check Answer: [17]
    1. NaI + Cl2 → ?
    2. AgCl + Au → ?
  10. Use the periodic table or the activity series to predict if each single-replacement reaction will occur and, if so, write a balanced chemical equation.
    1. Pt + H3PO4 → ?
    2. Li + H2O → ? (Hint: treat H2O as if it were composed of H+ and OH− ions.)
  11. Assuming that each double-replacement reaction occurs, predict the products and write each balanced chemical equation. Check Answer: [18]
    1. Zn(NO3)2 + NaOH → ?
    2. HCl + Na2S → ?
  12. Assuming that each double-replacement reaction occurs, predict the products and write each balanced chemical equation.
    1. Ca(C2H3O2)2 + HNO3 → ?
    2. Na2CO3 + Sr(NO2)2 → ?
  13. Assuming that each double-replacement reaction occurs, predict the products and write each balanced chemical equation. Check Answer: [19]
    1. Pb(NO3)2 + KBr → ?
    2. K2O + MgCO3 → ?
  14. Assuming that each double-replacement reaction occurs, predict the products and write each balanced chemical equation.
    1. Sn(OH)2 + FeBr3 → ?
    2. CsNO3 + KCl → ?
  15. Assuming that the double-replacement reaction occurs, predict the product and write a balanced chemical equation. Check Answer: [20]
    1. Pb(NO3)2 + KBr → ?
  16. Assuming that each double-replacement reaction occurs, predict the products and write each balanced chemical equation. Check Answer: [21]
    1. K3PO4 + SrCl2 → ?
    2. NaOH + MgCl2 → ?

Attribution & References

Except where otherwise noted, this page is adapted by Adrienne Richards from:

  1. An equation is balanced when the same number of each element is represented on the reactant and product sides. Equations must be balanced to accurately reflect the law of conservation of matter. ↵
  2. (a) [latex]\text{PCl}_5(s) + \text{H}_2 \text{O}(l) \longrightarrow \text{POCl}_3(l) + 2\text{HCl}(aq)[/latex]; (b) [latex]3\text{Cu}(s) + 8\text{HNO}_3(aq) \longrightarrow 3\text{Cu(NO}_3)_2(aq) + 4\text{H}_2 \text{O}(l) + 2\text{NO}(g)[/latex]; (c) [latex]\text{H}_2(g) + \text{I}_2(s) \longrightarrow 2\text{HI}(s)[/latex]; (d) [latex]4\text{Fe}(s) + 3\text{O}_2(g) \longrightarrow 2\text{Fe}_2 \text{O}_3(s)[/latex]; (e) [latex]2\text{Na}(s) + 2\text{H}_2 \text{O}(l) \longrightarrow 2\text{NaOH}(aq) + \text{H}_2(g)[/latex]; (f) [latex]\text{(NH}_4)_2 \text{Cr}_2\text{2O}_7(s) \longrightarrow \text{Cr}_2\text{O}_3(s) + \text{N}_2(g) + 4\text{H}_2 \text{O}(l)[/latex]; (g) [latex]\text{P}_4(s) + 6\text{Cl}_2(g) \longrightarrow 4\text{PCl}_3(l)[/latex]; (h) [latex]\text{PtCl}_4(s) \longrightarrow \text{Pt}(s) + 2\text{Cl}_2(g)[/latex]; ↵
  3. (a) [latex]\text{CaCO}_3(s) \longrightarrow \text{CaO}(s) + \text{CO}_2(g)[/latex]; (b) [latex]2\text{C}_4 \text{H}_{10}(g) + 13 \text{O}_2(g) \longrightarrow 8\text{CO}_2(g) + 10\text{H}_2\text{O}(g)[/latex]; (c) [latex]\text{MgCl}_{2}(aq) + 2 \text{NaOH}(aq) \longrightarrow \text{Mg(OH)}_2(s) + 2 \text{NaCl}(aq)[/latex]; (d) [latex]2\text{H}_2 \text{O}(g) + 2 \text{Na}(s) \longrightarrow 2\text{NaOH}(s) + \text{H}_2(g)[/latex]; ↵
  4. (a) [latex]\text{Ba(NO}_3)_2[/latex] , [latex]\text{KClO}_3[/latex]; (b) [latex]2 \text{KClO}_3(s) \longrightarrow 2 \text{KCl}(s) + 3\text{O}_2(g)[/latex] ; (c) [latex]2 \text{Ba(NO}_3)_2(s) \longrightarrow 2\text{BaO}(s) + 2\text{N}_2(g) + 5\text{O}_2(g)[/latex] ; (d) [latex]2 \text{Mg}(s) + \text{O}_2(g) \longrightarrow 2 \text{MgO}(s)[/latex]; [latex]4\text{Al}(s) + 3\text{O}_2(g) \longrightarrow 2\text{Al}_2 \text{O}_3(g)[/latex]; [latex]4\text{Fe}(s) + 3\text{O}_2(g) \longrightarrow 2\text{Fe}_2 \text{O}_3(s)[/latex]; ↵
  5. a. not composition; b. composition ↵
  6. a. composition; b. composition  ↵
  7. a. not decomposition; b. decomposition ↵
  8. a. not decomposition; b. decomposition ↵
  9. a. combustion; b. combustion ↵
  10. a. combustion; b. combustion ↵
  11. Yes; 2 H2 + O2 → 2 H2O (answers will vary) ↵
  12. a.   C4H9OH + 6 O2 → 4 CO2 + 5 H2O b.   4 CH3NO2 + 3 O2 → 4 CO2 + 6 H2O + 2 N2 ↵
  13. One element replaces another element in a compound. ↵
  14. a. Zn + Fe(NO3)2 → Zn(NO3)2 + Fe   b. 3 F2 + 2 FeI3 → 3 I2 + 2 FeF3 ↵
  15. a. Sn + H2SO4 → SnSO4 + H2  b. 2 Al + 3 NiBr2 → 2 AlBr3 + 3 Ni ↵
  16. a. No reaction occurs. b. . Fe(NO3)3 + Al → Al(NO3)3 + Fe ↵
  17. a. 2 NaI + Cl2 → 2 NaCl + I2  b. No reaction occurs. ↵
  18. a. Zn(NO3)2 + 2 NaOH → Zn(OH)2 + 2 NaNO3   b. 2 HCl + Na2S → 2 NaCl + H2S ↵
  19. a. Pb(NO3)2 + 2 KBr → PbBr2 + 2 KNO3  b. K2O + MgCO3 → K2CO3 + MgO ↵
  20. . a. Pb(NO3)2 + 2 KBr → PbBr2(s) + 2 KNO3 ↵
  21. a. 2 K3PO4 + 3 SrCl2 → Sr3(PO4)2(s) + 6 KCl  b. 2 NaOH + MgCl2 → 2 NaCl + Mg(OH)2(s) ↵

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Enhanced Introductory College Chemistry Copyright © 2023 by Gregory Anderson; Caryn Fahey; Jackie MacDonald; Adrienne Richards; Samantha Sullivan Sauer; J.R. van Haarlem; and David Wegman is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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